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using LT1512 for charging 4 batteries in series


I want to build NiMH battery charger for 4 cells series connected(final voltage is about 5.6v). In addition, my plan is that using the mobile phone charger(its output is 5v)to charge the series battery package.  In this situation , following  the reference design provided in the datasheet  page 1,  can the LTC1512  work well (ie. can the battery package  be full charged)?

thank you! 

  • The LT1512 should work well for your application.  SEPIC converter will properly boost the input voltage to 5.6V with the proper resistor-divider network from the battery to the FB pin.  Charging current will be set by the sense resistor in series with the coupled-inductor secondary.  A simple RC LPF is added from the sense resistor to the IFB input.  The IFB input regulates to 100mV.  Maximum charging current is ~1A.

  • hi,WATaylor. Sorry to disturb you, because there is another question about LT1512.  When the NiMH battery is full and its voltage is charged to 5.6v, can the LT1512 stop charging automatically? Because I viewed the total datasheet,there is no mention about the chip how to work after the battary fulled charged.

    Thank you

  • The LT1512 includes both battery-voltage and charge-current sensing.  (FB, IFB pins).  The battery is charged at constant current until the FB pin voltage reaches 1.245V.  As long as the battery is connected and input power is present, the LT1512 will add charge to the battery as required to maintain FB=1.245V.

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